The cactus is home to South America and Mexico, where they struggled with arid environments for a long time and finally took root in the desert. To adapt to the environment, the ancestors of the cactus changed, the leaves disappeared and the stems became fleshy and juicy with thorns. This change is beneficial to the survival of cactus plants.
Plants are known to require a lot of water, but their transpiration consumes most of the water. In order to reduce the loss of water, the ancestors of cacti gradually degenerated the leaves and even became needle-like or thorn-like, thereby reducing the transpiration area. Cactus is very water-efficient, some people compared apple trees and cacti together, and found that apple trees need to consume 10-20 kilograms of water per day, while cacti only need 20 grams, a difference of thousands of times. This difference is because cacti need to conserve water in order to adapt to arid environments.
If you put an apple tree with dense leaves in the desert, it will definitely not survive. The thorns of cacti come in many forms, some become white hairs, which reflect strong sunlight to lower the body surface temperature, and can also reduce the evaporation of water.
Cacti reduce the evaporation of water on the one hand, and store water in large quantities on the other hand. If enough water is not stored, cacti are threatened with death in deserts with scarce rain. The stem of the cactus becomes fleshy and juicy, with roots deep into the sand, able to absorb and store large amounts of water.
Because the fleshy stem of the cactus contains many colloidal substances, it has a strong ability to absorb water. The water storage capacity of cacti is very amazing, some cactus have fleshy stems up to 10 meters in diameter, as thick as a water tank, simply a huge reservoir. If thirsty, people can cut the cactus directly with a knife and drink the "drink" in the desert. It is through this morphological change that cactus plants adapt to arid environments. This is why cacti are fleshy and prickly.
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